The present invention relates generally to a tubular product made of a fiber composite material, and more particularly to a method for making the tubular product of the fiber composite material.
The tubular products, such as golf club, fishing rod, ski pole, etc., are generally made of a fiber composite material. There are currently the sheet-rolling method and the filament winding method, which are used to manufacture the tubular products. The sheet-rolling method involves the use of a plurality of fiber sheets which are preimpregnated with resin and are wound around a core shaft such that the fiber orientation forms a predetermined angle with the core shaft. The fiber sheets and the core shaft are heated and then cooled. A tubular product is finally formed by withdrawing the core shaft. The method allows the fiber sheets to be arranged in a way as desired. In light of some fibers being parallel to the longitudinal axis of the core shaft, the tubular product has a greater resistance to flexure. However, such a tubular product has a rigid spine that is formed at the junction of the ends of the fiber sheets which are wound on the core shaft. In addition, certain fiber sheets are wound irregularly. As a result, the tubular product so made is apt to have the uneven rigidity throughout the tubular product. The filament winding method involves the spiral winding of the fiber tows on a core shaft. The core shaft and the fiber tows are heated and then cooled. A tubular product is formed upon the withdrawal of the core shaft. The winding of the fiber tows on the core shaft is carried out with precision by a computer-aided technique. As a result, the tubular product has a uniformity in terms of physical properties. However, the tubular product is relatively less resistant to flexure in view of the fibers forming with the longitudinal direction of the core shaft an angle ranging between 30 and 45 degrees. In other words, the fibers can not be so arranged that they are parallel to the longitudinal axis of the core shaft.
The primary objective of the present invention is to provide a method for making a tubular product of a fiber composite material. The method of the present invention is free from the shortcomings of the prior art methods described above.
The method of the present invention is a hybrid of the filament winding method and the sheet rolling method. In the first place, a tubular body of a predetermined length is formed of fiber by the filament winding method. The tubular body is then provided with a predetermined number of the preimpregnated fiber sheets by the sheet rolling method such that the fiber sheets are rolled around the entire surface or a predetermined surface of the tubular body, and that the fiber orientation of the fiber sheets forms a predetermined angle with the longitudinal axis of the core shaft, and further that the fiber orientation of certain fiber sheets is parallel to the longitudinal axis of the core shaft. The tubular body is heated and then cooled. Upon removal of the core shaft from the tubular body, a tubular product of the method of the present invention is attained.